Immunoglubulin for intravenous (IVIG) has been used for more than 15 years in patients with primary immunodeficiency diseases and has dramatically improved the health status of affected patients. In an effort to improve the quality, effectiveness, and safety of this product, IGIV-C, is purer than the previously licensed product, IGIV-S/D, more closely reflects the IgG subclass distribution found in plasma, and is treated with caprylate rather than solvent-detergent to inactivate viruses such as hepatitis. Preclinical analytical and in vivo animal models have demonstrated the similar physical, chemical and functional properties of IGIV-C to IGIV-S/D. This will be the first clinical trial to compare the pharmacokinetics and safety profile of IGIV-C with IGIV-S/D in patients with primary humoral immune deficiency.